This invention relates to a filament wound tubular member and more particularly to a reinforcement for an opening in the wall of a filament wound vessel.
Filament wound vessels are generally fabricated by winding a resin impregnated fibrous strand around a mandrel in a generally helical pattern in a number of superimposed layers. In some cases, the strand is wound over rounded or curved ends on the mandrel to form the heads of the vessel integral with the cylindrical wall or shell. In other cases, the heads are formed separately and are secured by an adhesive within the open ends of the helically wound cylindrical shell.
Openings are normally provided in the shell or heads for fittings used for the introduction and removal of fluids or for the insertion of instruments or nozzles. The openings are normally made by cutting out the structural filamentary material after the vessel has been fabricated and cured. Since the stress resulting from internal pressure results in tension loads in the fibrous material of which the shell or wall of the vessel is composed, the holes cut in the wall will sever the load carrying filaments so that suitable means must be provided for transmitting the tension loads around the cut openings. Without means for transmitting the tension loads around the openings, the wall of the vessel would be greatly weakened in the area surrounding the opening.
In the past, fibrous patches bonded with a thermosetting resin have been applied to a vessel wall surrounding the openings therein as described in U.S. Pat. No. 3,106,940. According to this patent, one or more circumferentially wound annular patches are positioned in alignment with the location of the opening to be formed in the vessel wall and additional layers of the fibrous material are then wound or laid up over the patch. In the final cured vessel, the patch is embedded within the wall of the vessel, and the opening is then cut through the patched area.
Other methods included adhering a series of reinforcement patches around the opening after the opening had been cut through the wall.